The researchers came to this inclusion through a rather simple experiment:

First, they uploaded videos to YouTube and then bought YouTube ads targeting those videos. They also created a legion of bots to view the videos they had uploaded.

Even though the bots "viewed" two of the videos 150 times, YouTube's public view-counter only listed 25 of the views. Its system had apparently identified the rest of the views as fake and so weeded them out.

Google's Adwords ad platform, however, charged the researchers for 91 views — indicating that some views that it didn't deem real enough to count in the view-counter clearly counted against advertisers.

That doesn't look good for YouTube. If the company charges advertisers for fake views, they will be less likely to want to shell out their money.

Google sent the following statement on the report:

We’re contacting the researchers to discuss their findings further. We take invalid traffic very seriously and have invested significantly in the technology and team that keep this out of our systems. The vast majority of invalid traffic is filtered from our systems before advertisers are ever charged.

But at least in this case, 59 robo-views filtered out of the 150 views in the experiment doesn't seem like a vast majority.